To get the fix in, we need test coverage. However, I'm not sure if we should add more NG specific tests as we want to merge all *NG files back into * anyway and I assume that we're going to stumble over this sooner or later when doing the real conversions.

Yeah. I didn't expect that it would happen that fast, but #293318: Convert Aggregator feeds into entities did run into that problem and I fixed it over there. That means we also have test coverage for it, so closing this issue as a duplicate.